Network address translating network nodes are known from the prior art, which are known in technical literature as NAT (Network Address Translation). With a network address translation, “local”, in other words addresses valid only within a first local network area, are translated for a communication with network elements of an external second network area. The respective address of the sending network element and/or of the network element intended for receipt is used and/or replaced as a sender and/or destination address.
A method is also known, with the aid of which network elements within a network area can first determine whether the actual network area is delimited by a network address translating network node and with the aid of which a traversal of the actual network area is assisted. Such a method is also known as STUN (Simple Traversal of UDP over NATs).
One essential operation of the STUN protocol consists in a request of the actual public network address directed at the STUN server. In addition, a request for port numbers which were allocated for the request in network address translating network nodes is also possible. In this way STUN assists with an allocation of a network address which is valid for the transportation of the following messages e.g. IP address (Internet Protocol) and a port number.
The afore-described allocation is problematical in some instances, in which a communication terminal is connected to several external communication terminals. Such a constellation occurs for instance if a local network has a plurality of accesses to the worldwide data network by way of a so-called ISP (Internet Service Provider) and the communication terminal in this way has to use a plurality of public network addresses in order to communicate with a plurality of external communication terminals by way of the different network address translating network nodes.